The svelte, brown, undulating creature was dancing on the old, uneven stones of an ancient field wall.

Lissom-spined, it moved swiftly, and then slid out of sight. I followed the stoat into a small, coastal field where the object of its concentration would be, I assumed, a grazing rabbit. But it had also spotted me.

The little fields at Helvick Head in Co Waterford are implanted in memory from a time when I had a garden there, especially ridges of the best potatoes I had ever grown. A hare might jump over the outstretched legs of a visitor sitting on steps in the sun, a family of choughs might make strange cries overhead, but seeing a stoat, or "weasel" (duine usuail), was not an everyday event.

In the field, the animal turned to confront me in a kind of challenge. I had heard of such behaviour and there was a similar frisson as when, as a boy, I had once with a spade cornered a rat in a shed. A loft with my pigeons was overhead. The rat leaped up towards the descending implement.

The fearless stoat, much like the behaviour of American mink (an escaper now an established member of the Irish fauna), was indicating that I should clear off. A rabbit in the centre of the field was startled. We all moved away.

I had heard of stoats showing no fear of man who might come upon them as they passed through fields in family groups, moving homes, the females carrying young in their mouths, leaving them and going back for others, one by one. I once received a letter describing a 'stoat funeral' when a reader saw a group carrying a dead comrade for burial, much as foxes have been seen scraping earth and leaves over bodies of mates.

Last week, a regular reader, PG of Meath, sent me a picture of a salmon head, the body having been devoured - judging by tracks - by an otter along the Boyne. Stoats that eat small mammals and birds' eggs are also fish hunters, overcoming the limitations of small forepaws.

In a new book, naturalist and artist Gordon D'Arcy tells of seeing one at the Flaggy Shore in The Burren in 2002 repeatedly returning to a rocky cleft with a small fish (a goby or blenny) in its mouth, probably feeding youngsters. Stoats are brazenly fearless. D'Arcy writes that rod anglers "watched in amazement" as a stoat dragged a mackerel as big as itself across a rocky ledge and down a 'grike'.

The Irish stoat is one of two mammals which have been here since the Ice Age - the other is the hare. In 10,000 years of isolation, mustela erminea hibernicus has evolved into a distinct sub-species, visibly different from the British animal, being darker and with its cream underside more irregularly marked.

In northern Scotland, pure white or ermine stoats may be seen in winter, but piebald versions have turned up here. D'Arcy tells of a postman seeing an animal near Kinvara in 2014 "pure white with a black tail".

Many riveting observations are contained in D'Arcy's brilliant book of scenes from a place close to his heart. In The Breathing Burren (The Collins Press, Cork, €24.99), there are also beautiful, original watercolours of this unique area and its wildlife.